Object

ABSTRACT

Article whose surface exhibits a composite material in full or in parts, the composite material consisting of a non-metallic substrate containing at least one polymer, and a metallic layer present thereon and deposited without external current, having an adhesive strength of at least 4 N/mm 2 , the boundary layer present between the non-metallic substrate and the metallic layer exhibiting a calcium content, determined by EDX analysis of a microtome section, of maximum 0.5 % by wt., based on an analysis area of 1×1 μm whose centre runs through the boundary layer.

The present invention relates to an article whose surface consists of acomposite material in full or in parts, the composite materialconsisting of a polymer, and a metallic layer present thereon.

Such articles are known and used in particular in the decorative areasuch as e.g. chrome-plated articles made from ABS(acrylic/butadiene/styrene polymers) or polymer blends, in particulardecorative mouldings, showerheads, radiators grills of motor vehicles,coffee pots.

Such composite materials do not exhibit any noteworthy adhesive strengthsuch that—independently of the decorative properties—such articles areincapable of executing any technical functions in the sense ofprotection against wear and tear, anticorrosion protection,reinforcement, protection against mechanical, thermal and/or chemicalstress.

Recently, the possibilities have been considered of developing compositematerials or surfaces of such composite materials with such functions.

One process for the production of such layers is thermal spraying. Inthis case, metallic particles are heated and applied in an acceleratedmanner onto the substrate to be coated. In this way, metallic layers canbe produced on plastics. By means of this process, it is possible,however, to coat only structural parts with a simple geometry. The maindisadvantages of this process consist, moreover, of the fact that thelayers exhibit a high porosity, a high inherent stress, a high layerthickness and insufficient adhesion for structural parts subject to highmechanical stresses.

A further possibility for producing such composite materials consists ofthe vapour deposition of metal on plastic in a vacuum (CVD/PVD process).In this way, closed, metallic coatings are applied onto non-metallicsubstrates such as e.g. plastics. However, this process is economicallyunsuitable for structural parts with fairly large dimensions. Moreover,structural parts with indentations or voids are not completelymetallised. The articles produced in this way have a metal layer with athickness of maximum 3 μm which is insufficient for many industrialapplications. Moreover, these composite layers have only a very lowadhesive strength.

A wide-spread field of application for this vapour deposition techniqueis coating of plastic films, e.g. for food packaging. Thus, DE 198 49661 A1 discloses the vapour deposition of aluminium onto a specialpolyester film in such a way that it exhibits a strong oxygen barrier, ahigh gloss and a low coefficient of friction. The adhesive strengths ofup to 3 N/mm indicated therein, however, are too low to withstand to afunctional application, subject to mechanical stress, of the metallisedfilm.

In DE 43 12 926 A1, a process for the improvement of the adhesivestrength of dental metal-polymer composite layers is described. For thispurpose, a metallic substrate onto which a polymer has already beenapplied is irradiated with a special Te—CO₂ laser. If necessary, anadhesive agent is additionally used. A metallisation of plasticsubstrates is not described here.

DE 42 11 712 A1 also describes the irradiation of the surface of asubstrate in order to improve the adhesive strengths with an Eximerlaser. A PET (polyethylene terephthalate) film is irradiated with thisspecial laser in order to subsequently apply a ferromagnetic metal layerby vapour deposition within the framework of a PVD process. Such filmsare used as audio or video recording medium, among other things.

In addition, a process exists for special plastics in the case of whichthe articles to be coated are first caused to swell with suitablesubstances and subsequently etched chemically. The adhesive strengths ofthe metal layer applied onto the plastic, which are thus achieved,amount to maximum 2 N/mm².

A major disadvantage of this process is the considerable environmentalpollution by the two chemical treatment agents such that this processcan not be much longer for considerations of environmental politics.

A process, which has been developed further, for metallising polyamideswhich is based on the principle, described above, of causing the surfaceof the plastic substrate to swell but does not provide for pickling withchromium sulphuric acid is presented in an article by G. D. Wolf and F.Fünger “Metallisierte Polyamid-Spritzguβteile” (metallised polyamideinjection-moulded parts), Kunststoffe, 1989, pages 442-447. The surfaceof the amorphous polyamide is treated with an organometallic activatorsolution. Subsequently, a conventional plating process for depositing achemical nickel layer is carried out.

A disadvantage of this type of surface treatment which is based on achemical reaction of the treatment solution with the substrate is thatthe swollen surfaces are highly sensitive to environmental influencessuch as e.g. dust embedments. Moreover, the polyamide to the treatedmust be amorphous since partially crystalline or crystalline polyamidesare not attacked by the method presented. Consequently, this method is atime-consuming, expensive process which has only limited use in order toachieve adhesive composite layers between the polymer substrate andmetal layer.

Moreover, it is known from the thesis by H. Sauer, Siegen 1999 toproduce composite materials of a plastic and a metal layer presentthereon, the plastic surface, being roughened, before the application ofthe metallic layer, by using a blasting agent and subsequently treatedwith a special ethanol/calcium carbonate suspension.

Such composite materials exhibit an extraordinarily high adhesivestrength of the metal layer on the plastic substrate.

However, no fairly large surfaces can be produced on an industrial scaleby the process described therein. Moreover, the layers which can beobtained in this way have the disadvantage that small quantities ofcalcium carbonate remain in the boundary layer between the plasticsubstrate and the metal layer such that a “predetermined breaking point”is formed. This “predetermined breaking point” leads to the adhesivestrength varying greatly at different points of an article. Thesedeviations cause the points with the lowest adhesive strengths to causeto early defects in the case of articles subject to high mechanicalstress.

The object of the present invention consists of the provision of anarticle that can be subjected to extreme mechanical stress and whosesurface exhibits, partly or as a whole, a composite material consistingof at least one polymer and one metal layer, which composite materialovercomes the disadvantages of the state of the art described above.

The object is achieved according to the invention by way of an articlewhose surface exhibits a composite material, in full or in parts, thecomposite material consisting of a non-metallic substrate containing atleast one polymer, and a metallic layer present thereon and depositedwithout external current, having an adhesive strength of at least 4N/mm², the boundary layer present between the non-metallic substrate andthe metallic layer exhibiting a calcium content, determined by EDXanalysis of a microtome section, of maximum 0.5% by wt., based on ananalysis area of 1×1 μm, whose centre runs through the boundary layer.

It should be noted that, in a general embodiment, the non-metallicsubstrate essentially does not contain any particles of metal oxides ormetals. This means that no corresponding particles are detectableanalytically in the substrate in the microtome section at a depth ofmore than 10 μm below the boundary between the metallic layer and thenon-metallic layer.

On the other hand, it is possible for the boundary layer to containparticles of metal oxides or metals in small quantities up to a depth of10 μm, which originate e.g. from the blasting agent for roughening ofthe non-metallic substrate surface, for example.

In contrast thereto, it is possible in special embodiments in whichpolymers reinforced with glass fibre are used as non-metallic substrate,to detect, in the entire non-metallic substrate, particles of metaloxides in the microtome section. Commercial examples of such plasticsreinforced with glass fibre are Grivory HTV-6H1, Grivory HAT-PPA orGrivory GM-4H from EMS-GRIVORY. Commercial examples of plasticsreinforced with ceramics are Ryton BR111 and Ryton BR111 BL from ChevronPhillips Chemical Company LP.

Depending on the polymer-containing material used—the article can beproduced by so-called rapid prototyping processes, in particular bystereolithography or by laser sintering. In this way, complex shapes canbe produced within a short time which are coated evenly,contour-accurately with the metallic layer deposited without externalcurrent without reinforcements being observed in the edge area orweaknesses within the area of indentations or undercuts.

To determine the calcium content and the roughness values R_(a) andR_(z), a specimen is taken from the article according to the inventionand a microtome section is produced according to the method detailedbelow.

In a further embodiment, an object according to the invention ispreferred whose surface exhibits a composite material in full or inparts, this composite material exhibiting a first non-metallic layer anda second metallic layer applied thereon, and

-   -   a) the surface of the article not being chemically pretreated        before the application of the metallic layer deposited without        electric current; and    -   b) the metallic layer not being applied by thermal spraying,        CVD, PVD or laser treatment.

Chemical pretreatment should be understood here and subsequently, as adelimitation to mechanical treatments, any treatment of a substratesurface which is carried out by pickling, etching, swelling, vapourdeposition, plasma treatment, laser treatment or similar methods and inthe case of which a change to the surface is caused by a chemicalreaction.

In contrast to the articles of the state of the art metallised afterchemical pretreatment, the articles according to the present inventionexhibit a rough, sharp-edged boundary layer between the non-metalliclayer and the metallic layer applied without external current. Thesesharp edged indentations and undercuts of the boundary layer are clearlyrecognisable as edged surface contours, e.g. in a microtome sectionanalysis whose execution is described in the following. Thus, they canbe distinguished from the rather roundish, and in any case rounded-offcontours which are formed by a chemical pretreatment (FIG. 2).

When making the microtome section, there is the particular difficultythat the boundary surface between the substrate and the surface can bevery rapidly destroyed or detached by the treatment. To avoid this, anew separation disc from Struer, type 33TRE DSA No. 2493 is used foreach microtome section. Moreover, care must be taken to ensure that theapplication pressure which is transferred from the separation disc ontothe substrate coating is directed such that the force flows from thecoating in the direction towards the substrate. During the separation,care must be taken to ensure that the application pressure is kept aslow as possible.

The specimen to be examined is placed into a transparent embedding mass(Epofix putty, obtainable from Struer). The embedded specimen is groundin a table grinding machine from Struer, type KNUTH-ROTOR-2. Differentabrasive papers with silicon carbide and different granulations are usedfor this purpose. The exact sequence is as follows: Granulation TimeFirst grinding treatment P800 approximately 1 min Second grindingtreatment P1200 approximately 1 min Third grinding treatment P2400approximately 30 sec Fourth grinding treatment P 4000 approximately 30sec

During the grinding process, water is used in order to remove thegrinding particles. The tangential force which arises at thecross-section and by friction is directed in such a way that themetallic layer is pressed against the non-metallic substrate. In thisway, the metallic layer is effectively prevented from detaching itselffrom the non-metallic substrate during the grinding process.

Subsequently, the specimen thus treated is polished with a motor-drivenpreparation device of the DAP-A type from Struer. For this process, itis not the usual specimen mover which is used but the specimen isinstead polished exclusively by hand. Depending on the substrate to bepolished, a torque of between 40 to 60 rpm/min and an application forcebetween 5 and 10 N is used.

The microtome section is subsequently subjected to SEM micrography. Forthe determination of the boundary line enlargement, the boundary line ofthe layer between the non-metallic substrate and the metallic surface isdetermined with a 10,000 fold magnification. For the evaluation, theOPTIMAS program from Wilhelm Mikroelektronik is used. The result isdetermined in the form of the X-Y value pairs which describe theboundary line between the substrate and the layer. To determine theboundary layer magnification in the sense of the present invention, adistance of at least 100 μm is required. The course of the boundarylayer needs to be determined with at least 10 measuring points per μm inthis case. The boundary layer magnification is determined from thequotient of the true length by the geometric length. The geometriclength corresponds to the distance of the measured distance, i.e.between the first and the last measuring point. The true length is thelength of the line which passes through all the measuring pointsrecorded.

The surface roughness value R_(a) is determined according to thestandard DIN 4768/ISO 4287/1 again using the X-Y value pairs recordedbefore.

The R_(a) value is a measure reproducible by measuring techniques of theroughness of surfaces, profile runaways (i.e. extreme troughs orelevations) being largely ignored in the surface integration.

The adhesive strengths (indicated in N/mm²) of the composites accordingto the invention are determined exclusively by way of the frontaltensile test according to DIN 50160:

The frontal tensile test (vertical tensile test) according to DIN 50160has been used for many years for testing semiconductors, thedetermination of the adhesive tensile strength of thermally sprayedlayers and in various coating techniques.

For the determination of the adhesive strength by the frontal tensiletest, the layer/substrate composite to be tested is bonded between twotest dies and subjected to a load under a single-axis force up torupture (compare FIG. 1). If the adhesive strength of the adhesive isgreater than that of the coating and the rupture occurs between thelayer and the substrate, it is possible to calculate the adhesivestrength according to the equation$\sigma_{H\quad\exp} = \frac{F_{\max}}{A_{G}}$(with σ_(H exp): experimentally determinable adhesive strength, F_(max):maximum force on rupture of the composite and A_(G): geometric surfaceof rupture).

In the case of the basic materials according to the state of the artwhich hold a metallic layer on a microstructured plastic surface, tracesof calcium carbonate are detectable by the production process. Thesecontaminants are introduced by the necessary pretreatment using asuspension of ethanol and calcium carbonate. A possible explanation ofthe improved homogeneity of the adhesive strength in the case ofarticles according to the present invention can be considered as beingthat the remaining proportion of foreign components has been reduced insuch a way that it no longer acts as a separator or as a separatinglayer between the plastic surface and the metallic layer.

The determination of the proportion of calcium in the boundary surfaceis carried out by EDX spectroscopy.

Examples of such an article according to the invention are pump housingsand the corresponding rotors (pump wheel) of fuel pumps for the motorvehicle industry. These articles are those made of thermoplastics, inparticular of polyoxymethylene (POM) and polyphenylene sulphide (PPS).The phenol resin PF is used particularly preferably. Following thepretreatment described above, these fuel pump parts are coated withoutexternal current with a chemical nickel layer in a thickness of 5 μm.The corresponding articles according to the invention are characterisedby a particularly high protection against corrosion and wear and tear.The service lives of the articles thus produced are increased by afactor of 100—compared with the state of the art.

In a preferred embodiment of the present invention, the boundary layerbetween the non-metallic layer and the metallic layer exhibits aroughness with an R_(z) value of maximum 35 μm.

The R_(z) value is a measure of the average vertical surfacefragmentation.

According to a further embodiment of the present invention, thenon-metallic substrate contains at least one fibre-reinforced polymer,in particular a polymer reinforced with carbon fibre and the diameter ofthe fibre is less than 10 μm. According to a further embodiment of thepresent invention which is also preferred, the boundary present betweenthe non-metallic substrate and the metallic layer exhibits a roughnesswith an R_(z) value of maximum 100 μm and the non-metallic substratecontains at least one fibre-reinforced polymer, in particular a polymerreinforced with glass fibre, the diameter of the fibre being more than10 μm.

For the use of fibre-reinforced polymers whose fibre thickness amountsto more than 10 μm, in particular, it is important to achieve R_(z)values which are as low as possible. In the case of this combination itis, surprisingly, possible to achieve high adhesive strengths with—incomparison with the large fibre diameters used—low R_(z) values.

Insofar as the composite materials are subject not only to thermalstresses but also to mechanical stresses, reinforced plastics, inparticular plastics reinforced with carbon fibres (CRP), plasticsreinforced with glass (GFP) and also plastics reinforced with aramitefibres or plastics reinforced with mineral fibres are used particularlypreferably.

By providing these articles, a high rigidity of the resulting structuralparts is achieved with a low weight which structural parts are ofinterest for industrial application because of their low cost. Inparticular, polymers reinforced with glass fibre used as a component ofthe non-metallic layer exhibiting fibres with a diameter of more than 10μm are very cheap and easy to process. The fibre diameter has a stronginfluence on the roughness values such that, in the case of suchmaterials according to the present invention, a roughness value R_(a) ofmaximum 10 μm is achieved. At the same time, it is possible according tothe invention to achieve excellent values for the adhesive strength. Inaddition, the articles according to the invention have a highhomogeneity of adhesion. This makes it possible for the first time tosubstantially increase the service life of the structural part subjectto stress since even a local delamination of the composite materialleads to failure of the structural part as a whole. Of particular weightis the advantage in the case of structural parts with a surface coveredby the layer material of more than 10 dm², i.e. in the case of largestructural parts or structural parts with a large surface area.

In this way, articles with a high rigidity with a very low weight areobtained which exhibit an excellent adhesion of the metallic layer. Thisproperty profile is of interest for a wide area of technicalapplications such as e.g. the aircraft and space industry and for themotor vehicle industry.

According to a preferred embodiment, the non-metallic substrate issimultaneously the surface of the article. Preferably, these surfacesare based on a polymeric material. Fibre-reinforced plastics,thermoplastics and other industrially used polymers are to be mentionedas being particularly preferred.

Similarly, however, it is also possible to use articles whosenon-metallic substrate is not the surface of the article. Thus, thearticle can consist of a metallic or ceramic material which is coatedwith a non-metallic substrate which contains at least one polymer.Examples of such substrates are coated structural parts (e.g. explosionprotection for coated articles and anodised or hard anodised aluminiumstructural parts with a polymer layer present on the conversion layer.

According to a preferred embodiment, the standard deviation of theadhesive strength of the metal layer at six different measured valuepoints distributed over the surface of composite material amounts tomaximum 25%, in particular maximum 15%, of the arithmetic mean.

In this way, an even higher mechanical resistance to stress of theresulting structural parts is guaranteed.

The polymer of the non-metallic layer is preferably selected from thegroup of polypropylene, polytetrafluoroethylene, polyamide,polyethylene, polyvinyl chloride, polystyrene, epoxy resins, polyetherether ketone, polyoxymethylene, polyformaldehyde, polyacetal,polyurethane, polyether imide, polyphenyl sulphone, polyphenylenesulphide, polyarylamide, polycarbonate and polyimide.

In those cases in which the non-metallic layer contains eitherpolypropylene and/or polytetrafluoroethylene, adhesive strengths of atleast 5 N/mm² are achieved. This represents an excellent value, inparticular in combination with the high homogeneity of the adhesivestrength which could not be achieved previously.

It is thus possible for the first time to provide articles with acomposite material which exhibit particular properties with respect totheir wettability, their permeability for certain substances or alsowith respect to their compatibility with blood and blood plasma. Apossible application for such articles of polytetrafluoroethylene mightbe, for example, in medical technology as a membrane for pumps or infuel cell technology.

According to a further embodiment of the present invention, which isalso preferred, the metallic layer deposited without external current isa metal alloy or metal dispersion layer

In this way, articles with a composite material can be provided for thefirst time which exhibit an excellent adhesion of the non-metallic layerto the non-metallic layer. The homogeneity of the adhesion of themetallic layer also plays an important part for the suitability of thesearticles as structural parts subject to high stress for industrialmachines. This controlled selection of the non-metallic substrate andthe metallic layer present thereon allows an accurate adjustment of theproperty profile to the conditions of the field of use. It is thusimportant, for example, to adjust an accurately defined adhesivestrength in the case of CFP rollers which are used in a length ofbetween 1,000 and 12,000 mm, with a line load constant over their entirelength, for the roller to withstand the requirements for the entireservice life.

Particularly preferably, a copper, nickel or gold layer is applied ontothe non-metallic substrate of the article according to the invention asa metal layer deposited without external current.

However, a metal alloy or metal dispersion layer deposited withoutexternal current can also be applied, preferably a copper, nickel orgold layer with embedded non-metallic particles. In this respect, thenon-metallic particles may exhibit a hardness of more than 1,500 HV andmay be selected from the group of silicon carbide, corundum, diamond andtetraboron carbide.

These dispersion layers consequently have other functions, apart fromthe properties described above; for example, the resistance to wear andtear, surface wetting and emergency operation properties of the articlesaccording to the invention can be improved.

Also preferably, the non-metallic particles may exhibitfriction-reducing properties and be selected from the group ofpolytetrafluoroethylene, molybdenum sulphide, cubic boron nitride andtin sulphide.

In a further particularly preferred embodiment of the present invention,a layer of aluminium, titanium or their alloys is applied onto themetallic layer, deposited without electric current, of the articleaccording to the invention, the surface of the layer being anodicallyoxidised or ceramic coated.

Such layers of aluminium, titanium or their alloys oxidised or ceramiccoated by the anodic route are known on metallic articles and aremarketed under the trade name Hart-Coat® or Kepla-Coat®, for example, byAHC Oberflächentechnik GmbH & Co. OHG. These layers are characterised bya particularly high hardness and a high operating resistance andresistance to mechanical stresses.

Between the metallic layer of the article according to the inventiondeposited without electric current and the layer of aluminium, titaniumor their alloys, one or several further metallic layers can be arranged.

The further metallic layers ranged between the layer deposited withoutelectric current and the aluminium layer are selected according to theend purpose of use. The selection of such intermediate layers is wellknown to the expert and described e.g. in the book “DieAHC-Oberfläche—Handbuch für Konstruktion und Fertigung (The AHCsurface—Handbook for construction and manufacture”) 4^(th) enlargededition 1999.

It is also possible for the surface of such an article to be a ceramicoxide layer of aluminium, titanium or their alloys which is colouredblack by foreign ion embedment.

The ceramic oxide layer of aluminium, titanium or their alloys which iscoloured black by foreign ions is of particular interest for high valueoptical elements, in particular in the aircraft and aerospace industry.

The manufacture of ceramic oxide layers coloured black by foreign ionembedments has, for example, been described in U.S. Pat. No. 5,035,781or U.S. Pat. No. 5,075,178. The manufacture of oxide ceramic layers onaluminium or titanium is described e.g. in EP 0 545 230 B1. Themanufacture of anodically produced oxide layers on aluminium isdescribed e.g. in EP 0 112 439 B1.

The articles of the present invention are obtained particularlypreferably by means of a special process which comprises the followingsteps:

-   -   i. the surface of the non-metallic layer is not chemically        pretreated before applying the metallic layer applied without        electric current;    -   ii. the surface of the non-metallic layer is microstructured in        a first step by means of a blasting agent;    -   ii. the metallic layer is subsequently applied by metal        deposition without external current.

The articles according to the present invention exhibit, as compositematerial, first of all a non-metallic substrate which contains at leastone polymer. To produce the composite material according to theinvention, the surface of the non-metallic substrate is microstructuredin a first step by means of a blasting treatment. The process used isdescribed in DE 197 29 891 A1, for example. Inorganic particlesresistant to wear and tear, in particular, are used as blasting agent.Preferably, these consist of copper-aluminium oxide or silicon carbide.It has proven advantageous in this respect that the blasting agent has aparticle size of between 30 and 300 μm. Further suitable blasting agentsare steel and aluminium of different composition and granulation, glassblasting beads, corundum, ceramic beads, polymer resins, siliconcarbide, nut shells and other blasting agents know to the expert. It isfurther described therein that a metal layer can be applied by means ofmetal deposition without external current onto surfaces roughened inthis way.

As the designation of the process already indicates, no electric energyis supplied from outside during the coating process in the case of themetal deposition without electric current but instead the metal layer isdeposited exclusively by a chemical reaction. The metallisation ofnon-conductive plastics in a metal salt solution operating by chemicalreduction requires a catalyst at the surface in order to interfere withthe metastable equilibrium of the metal reduction bath there and todeposit metal on the surface of the catalyst. This catalyst consists ofnoble metal seeds such as palladium, silver, gold and occasionallycopper which are added onto the plastic surface from an activator bath.However, an activation with palladium seeds is preferred for processtechnology reasons.

Essentially, the activation of the substrate surface takes place in twosteps. In a first step, the structural part is immersed into a colloidalsolution (activator bath). In this respect, the palladium seedsnecessary for the metallisation and already present in the activatorsolution are adsorbed to the plastic surface. After seeding, the tin(II)and/or tin(IV) oxide hydrate which is additionally formed on immersioninto the colloidal solution is dissolved by rinsing in an alkalineaqueous solution (conditioning) and the palladium seed is exposed as aresult. After rinsing, nickel coating or copper coating can take placeusing chemical reduction baths.

This is effected in a bath maintained in metastable equilibrium by meansof a stabiliser, which bath contains both the metal salt and thereducing agent. The baths for the nickel and/or copper deposition havethe characteristic of reducing the metal ions dissolved therein at theseeds and to deposit elementary nickel or copper. In the coating bath,the two reactants must approach the noble metal seeds on the plasticsurface. As a result of the redox reaction taking place in this way, theconductive layer is formed, the noble metal seeds absorbing theelectrons of the reducing agents in this case and releasing them againwhen a metal ion approaches. In this reaction, hydrogen is liberated.After the palladium seeds have been coated with nickel and/or copper,the layer applied takes on the catalytic effect. This means that thelayer grows together starting out from the palladium seeds until it iscompletely closed.

As an example, the deposition of nickel will be discussed in furtherdetail here. During coating with nickel, the seeded and conditionedplastic surface is immersed into a nickel metal salt bath which permitsa chemical reaction to take place within a temperature range of between82° C. and 94° C. In general, the electrolyte is a weak acid with a pHof between 4.4 and 4.9.

The thin nickel coatings applied can be strengthened with anelectrolytically deposited metal layer. Coating of structural parts withlayer thicknesses of >25 μm is not economical because of the low rate ofdeposition of chemical deposition processes. Moreover, only a fewcoating materials can be deposited using the chemical depositionprocesses such that it is advantageous to make use of electrolyticprocesses for further industrially important layer materials. A furtheressential aspect consists of the different properties of layerschemically and electrolytically deposited with layer thicknesses of >25μm, e.g. levelling, hardness and gloss. The bases of electrolyticdeposition have been described e.g. in B. Gaida, “Einführung in dieGalvanotechnik” (Introduction into electroplating) “E.G. Leuze-Verlag,Saulgau, 1988 or in H. Simon, M. Thoma, “Angewandte Oberflächentechnikfür metallische Werkstoffe” (Applied surface technology for metallicmaterials) “C. Hanser-Verlag, Munich (1985).

Plastic parts which exhibit an electrically conductive layer as a resultof a coating processes applied without electric current differ withrespect to electrolytic metallisation only slightly from those of themetals. Nevertheless, a few aspects should not be disregarded in thecase of the electrolytic metallisation of metallised polymers. As aresult of the usually low conductive layer thickness, the currentdensity must be reduced at the beginning of electrolytic deposition. Ifthis aspect is ignored, a detachment and combustion of the conductivelayer may occur. Moreover, care should be taken to ensure thatundesirable layers of tarnish are removed by pickling baths particularlyadapted for this purpose. Moreover, inherent stresses may lead to thedestruction of the layer. In the case of deposits of nickel layers froman ammonia-containing bath, tensile stresses of the order of 400 to 500MPa, for example, may occur. By means of additives such as saccharineand butine diol, a change to the structure of the nickel coatings in theform of a modified grain size and the formation of microdeformations maypromote the decrease in internal stresses which may have a positiveeffect on a possible premature failure of the coating.

Examples of metal layers applied without external current are describedin detail in the handbook of AHC Oberflächentechnik (“DieAHC-Oberfläche” Handbuch für Konstruktion und Fertigung, (“The AHCsurface” Handbook for construction and manufacture”) 4^(th) edition1999).

In addition, one or several further layers, in particular metallic,ceramic and crosslinked or cured polymer layers can be arranged on themetallic layer of the article according to the invention.

It is thus possible, for example to apply a further electrolyticallydeposited nickel layer onto a nickel layer deposited without electriccurrent as metallic layer of the present invention and to deposit achromium layer thereon. The surfaces thus obtained can be applied ontorollers which are required to exhibit a high surface quality and a highmechanical load bearing capacity. The electrolytic deposition of thesecond nickel layer is preferably carried out in order to be able toproduce greater layer thicknesses cost effectively.

Moreover, the articles of the present invention can exhibit a copperlayer as metallic layer onto which subsequently a tin or a furthercopper layer can be applied. Subsequently a gold layer, for example, isapplied onto the existing metal layers. Such coatings can be used to EMVprotect electronic structural parts or to improve the thermalconductivity of the coated articles, for example.

Articles according to the invention can also exhibit a nickel layer asmetallic layer onto which a further nickel layer is applied. It ispossible in this way to achieve a high rigidity of the resulting plasticparts, thus guaranteeing an application for components subject to highmechanical stress such as gear wheels, suspensions or housing parts.

Moreover, a copper layer may be present as metallic layer on an articleaccording to the present invention which layer may be coated with anickel layer and subsequently with a chromium layer. A possibleapplication for such an article consists of using it as a mirror thatcan be rapidly positioned in copiers and in laser technology.

In a further practical example of the present invention, an epoxy resincan be applied onto a nickel layer deposited without electric current.The surface of this epoxy resin is subsequently once more coated with anickel layer. In this way, structural parts diffusion-resistantvis-à-vis hydrocarbons even under high pressure for the petrochemicalindustry can be produced such as e.g. piping and housings capable ofcompletely holding pumps.

An embodiment particularly preferred for industrial purposes consists offilter housings for high frequency components in the telecommunicationsindustry, in particular for transmitter mast units in the mobile radiotransmitter sector. These are articles of PPS/PEI whose entire surfaceis coated first with a nickel/phosphorus alloy applied chemicallywithout electric current in a layer thickness of 6 μm and subsequentlywith a silver layer applied electrolytically in a thickness of 6 μm.

Previously, such articles were made of aluminium and then nickel coatedand finally silver coated. These articles of the state of the artexhibit considerable corrosion problems, in particular in metropolitanareas polluted by waste gas. Previously, these filter housings had to bereplaced every 6 months. In the case of the article according to theinvention, the period of use, in contrast, can be extended to more than2 years.

Moreover, these further metallic layers which are applied onto existingmetallic layers of the article according to the invention can be appliednot only electrolytically but also by means of other processes such asCVD/PVD or thermal spraying onto an article with a metallic coatingaccording to the present invention.

In this way, it is possible to apply aluminium or stainless steel ontoan article which consists e.g. of plastic and has been provided with anickel layer according to the present invention.

A further interesting example of an article according to the inventionis a plastic which is provided first with a nickel layer applied withoutelectric current. Onto this nickel layer, layers of silver and gold aresubsequently electrolytically applied one after the other. Such a ratherspecific layer sequence is used in medical technology for structuralparts for diagnostic equipment.

Overall, the examples detailed above show that the articles according tothe invention can be used in a very large area of technicalapplications.

An article according to the present invention can, for example, consistof a roller for the sheet product processing industry (films, paper,textiles, printing), a structural part of turbomolecular pumps (ring forthe compressor stage), handle for household equipment (saucepans, lids),component for the aeroplane industry (handle, handrail) and the spaceindustry (sun sails), structural part for the electronics industry(condenser, sonic field condenser, sonic rider, microwave hollow-coredconductor, antenna, antenna housing), structural part for the moveablestructural parts of cyclones, wind sifters, structural part subject tomechanical, thermal and/or chemical stresses for the motor vehicleindustry (brake pistons for motor vehicles) or as a mould or componentfor the injection moulding industry.

EXAMPLE (ACCORDING TO THE INVENTION)

A panel of polyamide-6 with the dimensions 200×100×12 mm with an initialroughness of R_(a)=0.64 μm and R_(z)=7.5 μm was surface treated:

The surface pretreatment is carried out with a modified pressureblasting device from Straaltechnik International. The blasting device isoperated at a pressure of 4 bar. A boron carbide nozzle with a diameterof 8 mm is used as jet nozzle. The blasting period is 4.6 s. SiC withthe granulation P80 with an average grain diameter of 200 to 300 μm isused as blasting agent.

To adjust the blasting system specifically to the requirements of theplastic modification as regards reproducible surface topographies, 2pressure circuits were installed, one each for transporting the blastingagent and the actual acceleration process respectively. Thismodification gave a highly constant volume stream and a large pressurerange.

A stream of compressed air transports the blasting agent with a pressureas low as possible to the nozzle. The flow conditions guarantee a lowwear and tear of the unit and the blasting agent as a result of a highvolume stream of the blasting agent and a low proportion of compressedair. Only at the end of the conveying hose in front of the mixing nozzleis the cross section reduced in order to adjust the desired volumestream. In the case of all polymer pretreatments, a constant volume flowof 1 l/min was set. In the second part of the system, compressed air(volume stream 1) flows to the nozzle which can be adjusted steplesslywithin a pressure range of 0.2-7 bar. The blasting agent which isconveyed into the mixing nozzle at a very low flow rate is thenaccelerated by the high flow rate of the compressed air stream.

The panel roughened in this way is treated in an ultrasonic bath with amixture of deionised water and 3% by vol. of butyl glycol for fiveminutes.

The series of baths used for the metal deposition of the conductivelayer are based on the known colloidal palladium activation inassociation with a final catalysed metal reduction. All bath sequencesrequired for this purpose were purchased from Max Schlötter. Theimmersion sequences, treatment times and treatment temperaturesindicated by the manufacturer were maintained in all the process stepsof nickel deposition:

(1) Preliminary activator immersion solution:

-   -   This is used to avoid the entrainment of contaminants and to        completely wet the specimen before the actual activation of the        surface.    -   Immersion time: 2 min, room temperature

(2) Activator GS 510:

-   -   Activation of the surface with tin/palladium colloid.    -   Immersion time: 4 min, room temperature

(3) Rinsing bath: deionised water

-   -   To avoid the entrainment of activator GS 510 components by        rinsing in deionised water.    -   Immersion time: 1 min, room temperature

(4) Conditioner 101:

-   -   Conditioning of the material surface by removing undesirable tin        compounds from the surface.    -   Immersion time: 6 min, room temperature

(5) Rinsing bath: deionised water.

-   -   Immersion time: 1 min, room temperature

(6a) Chemical nickel bath SH 490 LS:

-   -   Metallising of the plastic with a light-coloured, semi-bright        amorphous layer at a separation temperature of 88-92° C.    -   Immersion time: 10 minutes

In the case of the selected immersion time in the nickel bath, a layerthickness of 1.4 μm was obtained. This thickness of the nickel layer issufficient for an electrolytic coating.

All process steps necessary for depositing the conductive layer tookplace in a plastic tubs holding 50 l, a bath temperature of 90°±0.5° C.being maintained throughout the entire coating cycle during the nickeldeposition by means of an additional hot plate with temperature control.In order to obtain a homogeneous and reproducible layer quality, theseries of baths were analysed and supplemented according to informationprovided by Max Schlötter after putting through 20 specimens.

After chemically applying the conductive nickel layer, the specimen wascooled in distilled water from approximately 90° C. to approximately 60°C. in order to be then coated further electrolytically with nickel at55° C. This intermediate step had the purpose of avoiding the formationof reaction layers and excluding inherent stresses caused by rapidcooling. The specimens which were coated exclusively with a conductivenickel layer cooled slowly to 25° C. in a distilled water bath.

The microtome section investigations by SEM (1,500 fold and 3,000 fold)are represented in the following figures (FIG. 3).

The evaluation of the EDX analysis gave a residual quantity of calciumof 0.03% by weight.

The results of the adhesive strength investigations are show in Table 1.TABLE 1 No. Adhesive Strength 1 20.5 N/mm² 2 19.5 N/mm² 3 13.4 N/mm² 416.4 N/mm² 5 22.3 N/mm² 6 20.3 N/mm² 7 16.8 N/mm² 8 14.5 N/mm² 9 13.2N/mm² 10 12.9 N/mm² 11 16.7 N/mm² 12 24.5 N/mm² 13 18.4 N/mm² 14 19.2N/mm² 15 15.4 N/mm² 16 22.9 N/mm² 17 16.7 N/mm² 18 17.3 N/mm² 19 12.8N/mm² 20 14.5 N/mm² 21 18.2 N/mm² 22 19.7 N/mm² 23 23.4 N/mm² 24 18.9N/mm² 25 20.1 N/mm² 26 21.4 N/mm² Standard deviation  3.4 N/mm² Mean18.1 N/mm² Coefficient of variation 19%

Comparative Example (Not According to the Invention)

The example according to the invention is repeated; however, after theblasting treatment the panel is treated in an ultrasonic bath, in asuspension of 5% by weight of CaCO₃ in 96% ethanol for 5 minutes.

Subsequently, the panel is treated in a further ultrasonic bath withpure 96% ethanol for a further five minutes.

The microtome section investigation by SEM (1,500 fold and 3,000 fold)are shown in the following figures (FIG. 4).

The evaluation of the EDX analysis gave me a residual quantity ofcalcium of 0.91% by weight which originates from the treatement of theCaCO₃/ethanol suspension.

The results of the adhesive strength investigations are shown in Table2. TABLE 2 No. Adhesive Strength 1 9.9 N/mm² 2 19.1 N/mm² 3 10.1 N/mm² 413.1 N/mm² 5 16.6 N/mm² 6 10.3 N/mm² 7 19.8 N/mm² 8 13.3 N/mm² 9 21.4N/mm² 10 10.9 N/mm² 11 20.0 N/mm² 12 10.9 N/mm² 13 11.7 N/mm² 14 13.0N/mm² 15 16.4 N/mm² 16 14.1 N/mm² 17 15.4 N/mm² 18 10.5 N/mm² 19 15.8N/mm² 20 16.7 N/mm² 21 8.5 N/mm² 22 17.2 N/mm² 23 7.0 N/mm² 24 18.2N/mm² 25 7.2 N/mm² 26 19.4 N/mm² Standard deviation 4.2 N/mm² Mean 14.1N/mm² Coefficient of variation 29.8%

The results clearly show a significant difference between the standarddeviation of the adhesive strength of the different measured valuedpoints distributed over the surface of the composite material.

During the manufacture of rollers for the printing industry, forexample, this difference causes rollers with a coefficient of variationof more than 25% to exhibit local detachments of the metal layer fromthe roughened plastic substrate during the necessary aftertreatment bygrinding which detachments are attributable to low adhesive strengths.

Comparable rollers according to the invention exhibit no detachmentsduring the grinding process.

LIST OF REFERENCE SYMBOLS OF FIG. 1

(1) Tensile die

(2) Adhesive

(3) Metal layer

(4) Substrate

1. Article whose surface exhibits a composite material, in full or inparts, the composite material consisting of a non-metallic substratecontaining at least one polymer, and a metallic layer present thereonand deposited without external current, having an adhesive strength ofat least 4 N/mm² characterised in that the boundary layer presentbetween the non-metallic substrate and the metallic layer exhibits acalcium content, determined by EDX analysis of a microtome section, ofmaximum 0.5% by wt., based on an analysis area of 1×1 μm whose centreruns through the boundary layer.
 2. Article according to claim 1 whosesurface exhibits a composite material in full or in parts, thiscomposite material exhibiting a first non-metallic layer and a secondmetallic layer applied thereon characterised in that a) the surface ofthe article is not chemically pretreated before the application of themetallic layer; and b) the metallic layer is not applied by thermalspraying, CVD, PVD or laser treatment.
 3. Article according to claim 1characterised in that the boundary present between the non-metallicsubstrate and the metallic layer exhibits a roughness with an R_(z)value of maximum 35 μm.
 4. Article according to claim 1, characterisedin that the non-metallic layer contains at least one fibre-reinforcedpolymer, in particular a polymer reinforced with carbon fibre and thediameter of the fibre is less than 10 μm.
 5. Article according to claim1 characterised in that the boundary present between the non-metallicsubstrate and the metallic layer exhibits a roughness with an R_(z)value of maximum 100 μm and that the non-metallic substrate contains atleast one fibre-reinforced polymer, in particular a polymer reinforcedwith glass fibre, and the diameter of the fibre is more than 10 μm. 6.Article according to claim 1 characterised in that the non-metallicsubstrate is the surface of the article.
 7. Article according to claim 1characterised in that the non-metallic substrate is not the surface ofthe article.
 8. Article according to claim 1 characterised in that thestandard deviation of the adhesive strength of the metallic layer at sixdifferent measured value points distributed over the surface of thecomposite material is maximum 25%, in particular maximum 15%, of thearithmetic mean.
 9. Article according to claim 1 characterised in thatthe polymer is selected from the group of polypropylene,polyterafluoroethylene, polyamide, polyethylene, polyvinyl chloride,polystyrene, epoxy resin, polyether ether ketone, polyoxymethylene,polyformaldehyde, polyacetal, polyurethane, polyether imide, polyphenylsulphone, polyphenylene sulphide, polyarylamide, polycarbonate andpolyimide.
 10. Article according to claim 1 characterised in that themetal layer deposited without external current is a metal alloy or ametal dispersion layer.
 11. Article according to claim 1 characterisedin that the metal layer deposited without external current is a copper,nickel or gold layer.
 12. Article according claim 10 characterised inthat the metal dispersion layer deposited without external current is acopper, nickel or gold layer with embedded non-metallic particles. 13.Article according to claim 12 characterised in that the non-metallicparticles exhibit a hardness of more than 1,500 HV and are selected fromthe group of silicon carbide, corundum, diamond and tetraboron carbide.14. Article according to claim 12 characterised in that the non-metallicparticles exhibit friction-reducing properties and are selected from thegroup of polytetrafluoroethylene, molybdenum sulphide, cubic boronnitride and tin sulphide.
 15. Article according to claim 1 characterisedin that, onto the metallic layer deposited without external current, alayer of aluminium, titanium or their alloys is applied whose surface isanodically oxidised or ceramics-treated.
 16. Article according to claim15 characterised in that one or several metallic layers are alsoarranged between the metallic layer deposited without external currentand the layer of aluminium, titanium or its alloys.
 17. Articleaccording to claim 15 characterised in that the surface of the articleis a ceramic oxide layer of aluminium, titanium or their alloys, whichlayer is coloured black by foreign ion embedments.
 18. Process for theproduction of an article according to claim 1 comprising the followingsteps: i. the surface of the non-metallic layer is not chemicallypretreated before applying the metallic layer deposited without electriccurrent; ii. the surface of the non-metallic layer is microstructured ina first step by a blasting agent; iii. the metallic layer issubsequently applied by metal deposition without external current. 19.Use of an article according to claim 1 as roller for the sheet productprocessing industry (films, paper, textiles, printing), a structuralpart of turbomolecular pumps (ring for the compressor stage), handle forhousehold equipment (saucepans, lids), components for the aeroplaneindustry (handle, handrail) and the space industry (sun sails),structural part for the electronics industry (condenser, sonic fieldcondenser, sonic rider, microwave hollow-cored conductor, circuitbreaker surface, antenna, antenna housing), structural part for themoveable structural parts of cyclones, wind sifters, structural partssubject to mechanical, thermal and/or chemical stresses for the motorvehicle industry (brake pistons for motor vehicles) or as a mould orcomponent for the injection moulding industry.
 20. Article according toclaim 16 characterised in that the surface of the article is a ceramicoxide layer of aluminium, titanium or their alloys, which layer iscoloured black by foreign ion embedments.